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• We present an electrochemical sensor for detecting DNA based on triblock DNA. • PolyA fragment has high affinity to the surface of Au electrode. • A wide linear range (10 pM-10 μM) was obtained with a detection limit of 2.9 pM. • The electrochemical sensor can detect DNA in human serum samples. Electrochemical aptasensor has been broadly advanced for nucleic acid detection. However, it is a long-term goal to design an aptasensor with high specificity, flexibility, and simplicity. In this work, we develop a strategy of triblock DNA probe, which consists of two DNA probes at both ends and ployA fragments in the middle as probe-polyA-probe. PolyA fragment has high affinity to the surface of gold electrode, so it can be assembled on the electrode surface via polyA instead of traditional Au-S bonds. When the target DNA is simultaneously hybridized with the two capture probes, the hybridization stability can be improved due to the strong base stacking effect. [Ru(NH 3) 6 ]3+, as signal probe, can be electrostatically adsorbed on the negatively charged DNA skeleton. A wide linear range (10 pM-10 μM) is obtained with a detection limit of 2.9 pM. Our electrochemical aptasensor has good repeatability, stability, and specificity. More importantly, the electrochemical sensor can successfully detect DNA in human serum samples, which proves its practical value and extensive applicability in complex environment. [ABSTRACT FROM AUTHOR]

A series of single-strand oligonucleotides functionalized catalytically active gold nanoparticle (AuNPs) as nonspecific receptors have been designed to build a protein sensing array. We take advantage of the correlation between the catalytic activity and the exposed surface area of AuNPs, i.e., DNA-proteins interactions mask the surface area of AuNPs, leading to poor catalytic performance of AuNPs. As the number of DNA-bound proteins increases, the surfaces of AuNPs become more masked; thus, the time of 4- nitrophenol/NaBH4 reaction for color change (yellow ? colorless) of the solution increases. Taking advantage of three nonspecific SH-labeled DNA sequences (A15, C15, and T15) as array sensing elements and the color-change time (CCT) of the solution as signal readout, colorimetric response patterns can be obtained on the array and identified via linear discriminant analysis (LDA). Eleven proteins have been completely distinguished with 100% accuracy with the naked eye at the 30 nM level. Remarkably, two similar proteins (bovine serum albumin and human serum albumin), two different proteins (bovine serum albumin and concanavalin) at the same concentration, and the mixtures of the two proteins with different molar ratios have been discriminated with 100%. The practicability of this sensor array is further validated by high accuracy (100%) identification of 11 proteins in human serum samples. [ABSTRACT FROM AUTHOR]

Herein, a label-free and highly sensitive electrochemical aptasensor for the detection of angiogenin was proposed based on a conformational change of aptamer and amplification by poly(diallyldimethyl ammonium chloride) (PDDA)-functionalized graphene/gold nanoparticles (AuNPs) composites-modified electrode. PDDA-functionalized graphene (P-GR) nanosheets as the building block in the self-assembly of GR nanosheets/AuNPs heterostructure enhanced the electrochemical detection performance. The electrochemical aptasensor has an extraordinarily sensitive response to angiogenin in a linear range from 0.1 pM to 5 nM with a detection limit of 0.064 pM. The developed sensor provides a promising strategy for the cancer diagnosis in medical application in the future. [ABSTRACT FROM AUTHOR]

Highlights: [•] A signal-off architecture for lysozyme detection was designed. [•] The sensor has a linear range (7–30nM) with a detection limit of 1nM. [•] The sensor shows a high sensitivity, good selectivity and satisfactory stability. [•] The sensor shows a great potential for practicable applications. [Copyright &y& Elsevier]

Highlights: [•] The preparation method of flower-shaped Ni/Al layered double hydroxide (LDH) is quite simple. [•] The Ni/Al-LDH has great adsorption capacity owing to its flower-shaped nature. [•] The very good linear relationship toward glucose can be obtained in two regions: 1–100μM and 0.5–21mM. [•] The sensor has a detection limit of 0.11μM. [•] The sensor possesses high sensitivity, good stability and excellent repeatability. [•] The sensor shows a great potential for practicable applications. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we described signal amplification architecture for electronic aptamer-based sensor (E-AB), which is applicable to a wide range of aptamers. Herein, we only take lysozyme as the representative sensing target. The amplification method was based on the network of thiocyanuric acid (TCA)/gold nanoparticles (AuNPs) modified with ssDNA. The binding event can be detected by a decrease in the integrated charge of the surface-bound [Ru(NH3)6]3+ which electrostatically absorbed onto the negatively charged phosphate backbones of DNA. In the presence of target molecules, a large amount of TCA/AuNP/ssDNA network associated with [Ru(NH3)6]3+ would be removed from the electrode surface, leading to a significant decrease of redox current. Cyclic voltammetry (CV) signals of [Ru(NH3)6]3+ provides quantitative measures of the concentrations of lysozyme, with a linear calibration ranging from 5pM to 1nM and a detection limit is 0.1pM. The detection limit of the proposed sensor is one order of magnitude and three orders of magnitude more sensitive than the detection limits in the absence of TCA (5pM) and in the absence of TCA/AuNP/ssDNA network (0.5nM). This amplification method is promising for broad potential application in clinic assay and various protein analysis. [Copyright &y& Elsevier]

Abstract: A highly sensitive and specific electrochemical aptasensor for Cu2+ detection based on gold nanoparticles (AuNPs) is presented. In this work, AuNPs offered a big surface area to immobilize a large number of aptamers and excellent electrochemical signal transduction. Its high sensitivity, low detection limit, and wide detection range are the main advantages over our former copper aptasensor. The peak current increased proportionally to the Cu2+ concentration over the range from 0.1nM to 10μM with a detection limit of 0.1pM. The presence of other divalent metal ions did not affect the detection of Cu2+, which indicates a high specificity of Cu2+ detection could be detected. Rapidity, simplicity, and excellent selectivity make it suitable for practical use in determination of Cu2+ from lake samples. [Copyright &y& Elsevier]

Abstract: A simple, highly sensitive, and label-free electrochemical impedance spectroscopy (EIS) aptasensor based on an anti-lysozyme-aptamer as a molecular recognition element, was developed for the detection of lysozyme. Improvement in sensitivity was achieved by utilizing gold nanoparticles (AuNPs), which were electrodeposited onto the surface of a gold electrode, as a platform for immobilization of the aptamer. To quantify the amount of lysozyme, changes in the interfacial electron transfer resistance (R et) of the aptasensor were monitored using the redox couple of an [Fe(CN)6]3−/4− probe. The R et increased with lysozyme concentration. The plot of R et against the logarithm of lysozyme concentration is linear over the range from 0.1pM to 500pM with a detection limit of 0.01pM. The aptasensor also showed good selectivity for lysozyme without being affected by the presence of other proteins. [ABSTRACT FROM AUTHOR]

Abstract: A one-step electrochemical sensor for sensing of potassium ion (K+) based on the conformational change of a single stranded DNA (ssDNA) with G-rich sequence was presented. The introduction of K+ induced folding of the aptamer, and the Fc moiety approached the electrode surface to produce measurable electrochemical signals. The aptasensor had a lower detection limit at 0.1nM, which was an excellent sensitivity compared with other methods for K+ detection. The proposed approach showed high selectivity and minimized the nonspecific adsorption, so that it was used for the detection of target K+ in the human serum sample. [Copyright &y& Elsevier]

A sensitive aptasensor for detection of l-histidine based on the switching structure of aptamer and gold nanoparticles–graphene nanosheets (GNPs–GNSs) composite was reported for the first time. The fabricated biosensor shows an expanded linear range, excellent sensitivity and selectivity against other amino acids. [ABSTRACT FROM AUTHOR]

We have proposed a colorimetric sensing assay exploiting the formation of gold amalgamation, combining with Hg 2+ mediated the growth of gold nanoparticles (AuNPs) for rapid detecting Hg 2+ ions with highly sensitivity and selectivity. In our developed approach, Hg 2+ is reduced to elemental mercury by citrate-capped AuNPs, forming gold amalgamation on the surface of AuNPs. AuNP-Hg 2+ interaction modulates the growth of AuNPs which is formed in the HAuCl 4 /NH 2 OH reaction. The rate of AuNP growth is highly dependent on the target concentration. AuNPs with low Hg coverage grow into spherical AuNPs with slow growth rate, which generates red-colored solutions. Whereas, AuNPs with high Hg coverage accelerate the growth of spherical AuNPs with a larger particle size, which generates blue colored solutions. At higher concentration, however, the growth rate of AuNPs begins to decrease. As the concentration of Hg 2+ increases till the saturation of Hg onto the surface of AuNPs, the growth of the AuNPs is inhibited due to full coverage of Hg on the AuNP surface. On the basis of this principle, Hg 2+ can be well determined ranging from 0.5 to 10 nM with a 0.26 nM of the detection limit. [ABSTRACT FROM AUTHOR]

The content of amino acids in human body is closely related to human health and plays an important role in physiological regulation and medical function. In order to recognize a variety of amino acids, an electrochemical sensor array based on poly(3,4-ethylenedioxythiophene) (PEDOT) electrode was established by using two kinds of electropolymerizers, i.e., citrate and the mixture of citrate and potassium nitrate as sensing elements. Different electropolymerizers lead result in different amount of negative charge on PEDOT electrode, which leads to different adsorption capacity for positive charge amino acids and different repulsion capacity for negative charge amino acids, bringing about obvious changes in differential pulse voltammetry (DPV) current. The five amino acids were accurately identified by linear discriminant analysis (LDA), and the electrochemical sensor array was successfully applied in the differential detection of amino acids in milk. [Display omitted] • 1. An electrochemical sensor array based on poly(3,4-ethylenedioxythiophene) electrode was established. • Citrate and the mixture of citrate and potassium nitrate as sensing elements of the sensor array. • The five amino acids were accurately identified by linear discriminant analysis. • The sensor array was successfully applied in the discrimination of amino acids in human urine. [ABSTRACT FROM AUTHOR]

Monitoring ascorbic acid (AA) levels in human body can provide valuable clues for disease diagnosis. Anchoring noble metal single atoms on perovskite substrate is a promising strategy to design electrocatalysts with outstanding electrocatalytic performance. Herein, we design an electrochemical method for detecting AA by utilizing Pt single atoms-doped CsPbBr 3 nanocrystals (Pt SA/CsPbBr 3 NCs) fixed on a glassy carbon electrode as an electrochemical catalyst. The uncharged 3,5,3′,5′-tetramethylbenzidine (TMB) undergoes oxidation to form the positively charged oxidized TMB (oxTMB) owing to the exceptional electrochemical catalytic performance of Pt SA/CsPbBr 3 NCs. Subsequently, the target AA reduces oxTMB to TMB, which is then electrocatalytically oxidized to oxTMB, producing significant oxidation current. In this way, such characteristic provides a sensitive electrochemical strategy for AA detection, achieving a concentration range of 50-fold with the detection limit of 0.0369 μM. The developed electrochemical method also successfully generates accurate detection response of AA in complex sample media (urine). Overall, this approach is expected to offer a novel way for early disease diagnosis. • The Pt SA/CsPbBr 3 was prepared as an electrochemical catalyst for AA detection. • The Pt SA/CsPbBr 3 microstructure contains 3 Pt–O and 1 Pt–Br bonds. • The detection limit of the sensor for electrochemical AA detection is 0.0369 μM. • The sensor achieved accurate detection of AA in complex urine sample. [ABSTRACT FROM AUTHOR]

• We developed an electrochemical sensor based on T-Hg-T aptamer and exonuclease III. to detect Hg2+ concentration. • We use exonuclease III to cleave dsDNA into ssDNA and 5′ -P single mononucleotides. • A good linear relationship between differential pulse voltammetry current and Hg2+ concentrations (1 pM-1 μM) was obtained. • The detection limit of Hg2+ is as low as 0.2182 pM. Mercury ion, as a kind of toxic ion, seriously endangers human health and ecological environment. It is necessary to establish an accurate and sensitive method for detecting Hg2+. In our work, we develop an electrochemical sensor for Hg2+ detection based on thymine-Hg2+-thymine (T-Hg2+-T) coordination. The cleavage of the double-stranded DNA with T-Hg2+-T pairs catalyzed by Exonuclease III (Exo III) is prompted to happen upon binding target Hg2+. [Ru(NH 3) 6 ]3+, which can be electrostatically adsorbed on the negatively charged DNA backbone, was used to convert the electronic signal. A wide linear range (1 pM-1 μM) was obtained with a detection limit of 0.22 pM, which meets the requirements of environmental sample analysis. In addition, the sensor also shows excellent selectivity for Hg2+ detection in the presence of other high-level interfering substances. More importantly, the electrochemical sensor could successfully detect Hg2+ in river water samples, demonstrating its promising potential for detecting Hg2+ in the real world. [ABSTRACT FROM AUTHOR]